Female electrical connectors



April 1967 A. E. POWELL 3,314,044

FEMALE ELECTRICAL CONNECTORS Filed Dec. 16, 1964 IO 20 11. Z '4 b -1|lllll All -'III;H II i 22 24 1 :1. .E. Z8 34 T 1 2 30 INVENTOR. fl saer f21u United States Patent 3,314,044 FEMALE ELECTRICAL CONNECTORS AlbertE. Powell, Binney Lane, Old Greenwich, Conn. 06870 Filed Dec. 16, 1964,Ser. No. 418,733 2 Claims. (Cl. 339-256) This invention relates tocontacts and more particularly to a female contact member for receivinga corresponding mating male member.

Contacts embodying the present concept are particularly adapted, :amongother possible uses, for use in conjunction with a male contact memberto establish a separable contact in an electrical circuit, and for usein coaxial connections where a constant cross-sectional configuration isdesirable in order to maintain constant ratios of internal to externaldiameters to provide constant impedance. The connection according tothis invention is also adapted for other devices whereever low contactresistance is desirable.

Heretofore, the usual female contact member used in conjunction with amale contact member to establish a separable contact comprised a rodhaving an internal bore extending inwardly from one end thereof. The rodwas then slotted inwardly from the same end forming a bifurcated head,the two ends being slightly crimped to frictionally receive a matingmale member. The disadvantage of such a contact resides in the fact thatthe only portion of the female member in contact with the male member isthe tips of the ends of the bifurcated head. Thus, the mechanicalgripping action is not very satisfactory and the electrical resistanceis high.

A feature of this invention resides in the provision of a new andimproved female contact member which has a relatively low electricalresistance, which may be fabricated from inexpensive materials, whichprovides good gripping action, and which provides a relatively largecontact area with a mating male contact member.

Another feature of this invention is the provision of a new and improvedfemale contact member which readily receives the mating male member butresists the withdrawal of the male member, which has superior axialalignment characteristics, which resists injury or damage due tocareless or improper handling, which has a long life, and which iscompact, convenient, practical and inexpensive to manufacture.

In essence, the present invention contemplates the provision of a femalecontact member for receiving a corresponding mating male member whereinthe female member comprises an elongated member having a substantiallycentrally disposed longitudinally extending bore commencing from one endthereof. There are a plurality of helically twisted or torsional gripmembers which serve as a portion of the elongated member, this portionbeing disposed coaxially with respect to the longitudinally extendingbore and spaced inwardly of the end of the elongate-d member. The gripmembers may have substantially parallel edges one with respect to theother which define a like plurality of longitudinally extending slots.The internal perimeter of the grip member is reduced prior to theinsertion of the male member. Subsequent to the insertion of the malemember, the female member expands to substantially the same dimensionsas the remainder of the elongated member.

In one form of the invention the female contact member for receiving acorresponding mating male member comprises a rod or tubular elementhaving a central bore extending inwardly a substantial distance from oneend thereof to receive said male member. A portion of the tubularmember, spaced inwardly with respect to the end thereof, is providedwith a plurality of helically twisted, radially resilient, grip membersformed by longitudinally slotting and axially twisting the tubularmember whereby upon insertion the male member is releasably retained incontact position.

The invention in another form thereof comprises a method ofmanufacturing a female contact member comprising taking a tubularmember, longitudinally slotting a portion of said member, fixed-1ygripping said tubular member at a first position while simultaneouslytwisting said member at a second position spaced from said firstposition along the longitudinal axis of said member, thereby neckingdown said tubular member for releasably retaining a male member incontact position upon insertion. The term neck down as used herein meansto reduce the diameter of the rod or tubular member along a portion ofthe longitudinal length.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception on which thisdisclosure is based may readily be utilized as a basis for the designingof other structures for carrying out the several purposes of theinvention. It is important, therefore, that the claims be regarded asincluding such equivalent constructions as do not depart from the spiritand scope of the invention. A specific embodiment of the invention hasbeen chosen for purposes of illustration and description, and is shownin the accompanying drawings, forming a part of the specification,wherein:

FIG. 1 is a longitudinal sectional view of a tubular member aftercompleting the initial steps employed in the fabrication of a contactmember in accordance with the concept of the invetnion;

FIG. 2 is a side elevation, partially in longitudinal :section, showinga vise and rotary collet gripping the contact member during thefabrication of a female contact member;

FIG. 3 is a side elevation of the female contact, mandrel, member, viseand rotary collet subsequent to the twisting of the member;

FIG. 4 is :a longitudinal sectional view of the female contact memberconstructed in accordance with the concept of this invention;

FIG. 5 is the female contact member of FIG. 4 in engagement with acorresponding mating male member; and

FIG. 6 is a transverse sectional view taken along the line 6-6 of FIG.5.

In the illustrated embodiment of the invention, the female contactmember designated generally at 10 (FIG. 1) comprises a tubular member 12which may be fabricated from a solid bar by means of drilling acentrally disposed longitudinally extending bore 14- therein. It

will be appreciated that the tubular member 12 may be manufactured usingbrass or other suitable inexpensive copper alloy as compared to thematerials required by the prior art devices which employed Phosphorbronze, beryllium copper, for example. Not only are such materials lessexpensive, but they are also easier to machine and Work as compared tomaterials required by the prior art. The tube 12 is provided with achamfer 16 at the entrance thereof 18 in order to guide the entry of amale probe to be used with this contact. A plurality of longitudinallyextending slots 20, 22 and 24 (FIG. 1) are disposed in radially spacedrelationship one with respect to the other about the tubular member 12,slots being milled or sawed in the wall of the tube 12, as desired.

As best seen in FIG. 2, a rod or mandrel 26 having a diameter slightlysmaller than the mating male contact to be used, is inserted in thetubular member 12 at least as far as the ends of the slots 20, 22 and24. The tubular member 12 is held or gripped by a vise 28 as at 30 (FIG.2). Still referring to FIG. 2, the end of the tubular member 12 isgripped by jaws 34- of a rotary collet 32.

As best seen in FIG. 3, the collet 32 is rotated while the vise member'28 is retained in a stationary or fixed position. This gives theelongated slots 20, 22 and 24 a helical or spiral-like configuration.The portion of the tubular member 12 adjacent the slots 20, 22 and 24necksdown until the inside diameter of this portion contacts the mandrel26 and is thereby limited from further necking-down. In effect themandrel 26 during the twisting operation of the collet 32 tends todirect the tubular member to conform to the outside diameter thereof andto form an elongated neck-down portion extending substantially thelength of the slots 20, 22 and 24. Thence the mandrel 26 is removed fromthe tubular member 12, the collet 32 is removed therefrom and the vise28 is released. The female contact member 10 is then in its final formand has the appearance as shown in FIG. 4.

Referring to FIG. 4, the portions of the tubular member 12 adjacent theslots 20, 22 and 24 are coiled gripping members 19 and 21 as shown. Itwill be appreciated that the gripping members 19 and 21 have asubstantially helical configuration and are torsionally defiected. Also,it is noted that the necked-down portion 36 is an elongated sectionhaving a substantially uniform internal diameter 38.

In order to make an electrical connection or contact a male contact 44(FIG. is inserted through the entrance 18 into the female contact 10. Itis noted that the chamfer 16 helps to align the male member 44 for in.sertion when contact is to be made. It will further be appreciated thatthe axial forces required to insert the male member are substantiallyless than the forces required to retract the male member. This is due tothe fact that during insertion the necked-down portion 36 of the tubularmember 12 is subjected to compression, one force acting towards theright as viewed in FIG. 5 by the male member 44 and the second (forceacting towards the left as viewed in FIG. 5 by the female member 10.These two forces tend to spread or open the slots 20, 22 and 24 andthereby increase the diameter 38 of the neckeddown portion 36.

On the other hand when the male member 44 is being retracted orwithdrawn from the female member 10, the necked-down portion 36 is undertension and hence this portion tends to reduce in diameter and therebygrip the male member tighter. Moreover, the gripping members 19 and 21are torsionally deflected and the internal surfaces tend to grip themale member 44 with a twisting-like grip. It will be appreciated thatwhen the male member 44 is fully inserted inthe female member theexternal diameter 36 of the grip member portion 19, 21 is substantiallyequal to the diameter 40 of the tubular member prevailing before thenecking-down or twisting operation. This provides a substantiallyconstant 4 cross-section, and here, provides a substantially constantimpedance.

Particular attention is directed to the large elongated contact surfacebetween the male member 44 and the female member 10. This factor is ofparticular significance not only for mechanical interlocking purposesbut also in providing a contact of low electrical resistance. Thefollowing table tabulates the physical dimensions of four differentsamples of female contact members constructed in accordance with theconcept of this invention. It will be appreciated that these contactsare given for illustrative purposes and not for purposes of limitation.

TABLE Example Tubular Member, Outside Dia.,

Mils 66 36 36 20 Tubular Member, Inside Dia., Mils. 50 20 25 12 TubularMember, Perimeter, Mils- 207 113 113 62. 8 Slot, Number 6 4 3 3 Slot,Width Mlls 10 6 5 4 Slot, Length, Mils 135 135 125 Total Width, AllSlots, Mils 60 24 15 12 Ratio, Total Width of all Slots/Tubular MemberPerimeter .29 .212 .133 191 Approximate Angle of Twist, De-

grees 120 120 120 Material Brass Brass Brass In general the slot shouldbe as long as possible because the longer the slot the less torsion isrequired to twist the tubular member. The relationship between the slotwidth, the number of slots, the perimeter of the tubular member and theangle of twist is of critical concern. The minimum twist of the arcuatemember is -a distance sufficient to neck-down the tubular member to aninternal diameter less than the internal diameter of the outsidediameter of the mating male member. The maximum twist of the tubularmember is an arcuate distance such that the tubular member necks down tothe point where the slots are substantially closed. If the tubularmember is twisted beyond this point the tension stress would tend tobreak the member. Preferably the angle of twist is of the order of about120 degrees. The range of the ratio of the total width of all slotsdivided by the tubular member perimeter is from about 12 to about 40percent and preferably is between about 13 percent and about 29 percent.

Referring in particular to Example No. 3 in the above table, the tubularmember was twisted against a mandrel having a diameter of 197 mils. Itwas tested with a male contact having an outside diameter of 20.5 milsand a length of 105 mils. This contact showed a resistance of 0.0027ohm, which compares to a resistance of 0.006 ohm for a similarbifurcated contact of the prior art, said prior art contact had thefollowing dimensions: external diameter 36 mils, internal bore prior tocrimping 25 mils, slot mils long extending from the open end of thecontact, the width of the slot 10 mils, crimped so that the two freeends just touched. It is noted that the prior art contact wasmanufactured from Phosphor bronze, and the contact according to thisinvention was manufactured from brass. The same male contact member wasused with the prior art device as was used in conjunction with Example 3of the device according to this invention. It will be furtherappreciated that the resistance of the device according to the presentinvention had a variation of less than 3 percent after 200 insertions ofthe male member.

It will thus be seen that the present invention does indeed provide animproved female contact member and a method of manufacturing same.

Although a particular embodiment of the invention is herein disclosedfor purposes of explanation, modifications thereof after study of thisspecification, will be apparent to those skilled in the art to which theinvention pertains. Reference should accordingly be had to the appendedclaims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A female electrical contact member for receiving a correspondingmating male electrical member, said female member comprising anelongated member having a substantially centrally disposedlongitudinally extending bore commencing from one end thereof, saidelongated member having an elongated necked-down tubular portion spacedinwardly from said one end, said portion having a substantially uniforminternal diameter less than the diameter of said bore, said portion ofsaid elongated member being provided with a plurality of resilienttorsional gripping members separated by slots, said gripping membersextend substantially the length of said portion and which are helicallytwisted through an angle of about 120 degrees, the summation of the slotwidth being a distance of between about 13 percent and about 29 percentof the perimeter of said elongated member prior to twisting, said slotsbeing substantially closed subsequent to twisting, whereby said grippingmembers exert a combination radial and torsional force upon the malemember when it is in its inserted position.

2. A method of manufacturing a female electrical contact member forreceiving a corresponding mating male electrical member, said methodcomprising taking an elongated member, forming an elongated centrallydisposed longitudinally extending bore commencing from one end thereof,removing about 13 percent to about 29 percent of a perimeter portion ofsaid member in the form of a plurality of spaced longitudinal slotscommencing inwardly of the end thereof, inserting a mandrel having anoutside diameter slightly smaller than said bore into said elongatedmember to a position adjacent said slots, torsionally deflecting saidmember through an angle of about 120 degrees to have the slotted portionconform to the outside diameter of said mandrel to form an elongatednecked-down tubular portion having .a substantially uniform internaldiameter less than the diameter of said bore, continuing said deflectinguntil said tubular portion extends to a longitudinal length greater thanpercent of the length of said slots, and removing said mandrel from saidelongated member.

References Cited by the Examiner UNITED STATES PATENTS 11/1931 Wilhelm.

10/1948 Sprigg 29-15555 12/1948 Bach et al 339-252 7/1951 Freeman29--508 X

1. A FEMALE ELECTRICAL CONTACT MEMBER FOR RECEIVING A CORRESPONDINGMATING MALE ELECTRICAL MEMBER, SAID FEMALE MEMBER COMPRISING ANELONGATED MEMBER HAVING A SUBSTANTIALLY CENTRALLY DISPOSEDLONGITUDINALLY EXTENDING BORE COMMENCING FROM ONE END THEREOF, SAIDELONGATED MEMBER HAVING AN ELONGATED NECKED-DOWN TUBULAR PORTION SPACEDINWARDLY FROM SAID ONE END, SAID PORTION HAVING A SUBSTANTIALLY UNIFORMINTERNAL DIAMETER LESS THAN THE DIAMETER OF SAID BORE, SAID PORTION OFSAID ELONGATED MEMBER BEING PROVIDED WITH A PLURALITY OF RESILIENTTORSIONAL GRIPPING MEMBERS SEPARATED BY SLOTS, SAID GRIPPING MEM-